Attempts will be made to identify the staphylocidal fatty acid (SFA) produced in staphylococcal abscesses. A newly detected fatty acid-modifying enzyme (FAME) will be purified and characterized. Antibodies to FAME will be examined to determine whether they are protective in the host. S. aureus strains will be examined to establish the incidence of FAME producing strains, and the amount of FAME produced in abscesses will be measured. Antibodies to staphylococcal lipase will be prepared and evaluated for their protective ability. Lipase-negative mutants of S. aureus will be compared with their parent strains for their ability to survive in abscesses. The production of lipase within abscesses will also be measured. The staphylococcal factor which can stimulate lipid accumulation in macrophages will be purified and characterized. We also intend to see whether macrophages are the source of SEA and triglyerides. Studies will be conducted to determine whether diabetes, steroid administration, ether inhalation, or delayed hypersenitivity can alter SFA or glceride production in abscesses. A competitive radioimmunoassay will be developed to measure the amount of S. aureus delta toxin produced in abscesses.